Obese and overweight women are gaining weight rapidly in low-and middle-income countries while those who are severely undernourished are not experiencing similar weight gains, according to a study by Harvard School of Public Health (HSPH) and University of Toronto researchers. This growing divide may force governments in the developing world to care for people who fall dramatically short on their calorie intake while simultaneously treating health problems associated with obesity, including diabetes and heart disease.

The study, published in the January 15, 2013 issue of PLOS Medicine, uses information collected in Demographic and Health Surveys (DHS), a project that tracks health and population trends in developing countries. Researchers analyzed the body mass index (BMI) of 730,000 women living in 37 countries between 1991 and 2008.

“The study is novel because for the first time we are showing that increases in BMI are not happening equally across the board; rather, increases in average BMI are largely driven by populations that are already overweight or obese, with little to no change among underweight individuals,” said senior author S V Subramanian, HSPH professor of population health and geography. “This divergence in the population with fat getting fatter and lean remaining lean is aligned with general patterns of divergence on other domains such as income and wealth, which of course are primary drivers of weight status in these countries.”